So here is the ongoing issue with my 2006 XK8 Victory Edition Coupe (yeah 1 of 53) with 54000 on it and it is as clean as a whistle: Simply put, very occasionally no crank, no start with several faults on the dash which I am fairly sure are just phantom faults. So far I think it only happens (not consistently) after a a longer ( 20+ miles drive). And I kid you not, one just has to wait and eventually it starts and bangs like a champ.

Here are the facts to fill your Jag-genius brainpans:

• Battery is kept on a good tender always and appears to be solid. 2-3 years old.
• Earth grounds check out.
• J-Gate module/ Neutral Switch replaces and shifter works as it should. It was busted but the problem persisted.
• Instrument cluster replaced with a professionally cloned and inspected replacement (it was flaking out).
• After locking with the fob, the security lock flashes/I keep it locked always.
• Codes I get at OBD only P1637 (CAN BUS).
• Relays all appear un-damaged.
• I was told by the sellers that this has been an issue for a good while. They said (and I can’t confirm) that the alternator was checked out OK and the starter was replaced (again, can’t confirm).

The car runs like a champ but I am itchy about the reliability give that once in a while she decides to no crank, no start out of the friggin' blue. My feeling is that this is as random as random can be. The scientist in me want to pin it to this plus that equals the problem…. And the solution eludes me and the “experts” I have taken it to.

I love the Jag community, there is enough collective brain power to light a city and I hope some of that light is shed on this guy.

 

One of the possible causes of this issue is a loose connection in the luggage compartment Junction Box:





The multi strand cables are also known to break at the crimped terminals.

Graham

 

I will double check. The random nature of this makes me think it is something like this... simple stuff.

 

Maaaaan,,, I have the same thing (may be the same thing) in a 2004 XKR and I've "isolated" it (kinda sorta, its horrible) to a signal wire from the trans to the starter relay OR a ground signal from the ECU to the starter relay... What a headache. Mine never works and I use a trigger I've wired INSIDE the car, lol

Try this (not a fix) the next time it acts up, remove/unplug the starter relay, remove the cover (in the RH enclosure) if ya can,,,, then go back and turn the key to the RUN position, leave it there, and go pinch the stater relay to make "contact" so the starter engages... I bet it will start up and run normally... Well maybe

At this point it's a shot in the dark, not definitely the issue and certainly not the right or complete solution - but it may be worth something... Just to start - no pun intended.

 

Interesting. I have a question.
Can you tell me more about pinching the relay?

 

Yeah. It's a little tricky to get the cap off. This is the square brown common relay that you will find throughout the XKs,,, but once you get it off and have the relay in your hand,,, take a good look at it and you'll see how there is a little contact point on a spring. Pinch-able to make contact. When excited, the coil in the relay becomes an electro magnet and pulls the spring loaded contact against is 12v contact. Hard to explain... You'll see it it.

Anyways, once you've figured out the "pinch",,, replace the relay, turn the key to ON, and give it a try.

One thing I should have mentioned is it MIGHT simply be that the relay is on its way out...? Maybe. That would be a good thing.

Another thing - sometimes the 6hp26 transmission will leak right at a seal and multi plug where the NEUTRAL safety signal (the signal wire mentioned earlier) originates and it will foul the 12v signal to the ECU for the "ok to start" signal - which will inhibit the ECU from grounding the starter relay to engage it. But that's (not a difficult) whole other kettle O fish.

 

Far out. I will look into both when I have it on my lift. No trans leaks I know of.... but will give a look.

 

The leak is often less than a dribble...very slow.

Anyways, I went off the deep end. The things Graham mentioned - that's where I would start... He's probably (and often is) right.

 

The mystery is the randomness and the self correction after waiting. I keep coming back to this.

 

Jeph,

Last week my 2005 XKR would not Start (Just out of the blue)....Tried it several times....Then "Bang", it started! ...Yesterday it would not Start again....Checked the little Box in the Boot that GGG noted and it is OK! But it still won't start....Now, I have to try JayJagJay's alternative....Could it be? I'm not much of an Electrician and only recently learned what a Relay is! So, I just called the Wrecker.....I'll let you guys know what the problem was when the Mechanic calls me with the details! What a "Bummer"!

Billy Clyde @ Cinco Ranch

 

Eagerly waiting to hear how this goes.

 

Same here!!!

 

I didn't see anyone mention the false bulkhead. I had the same issue on my 98 X308. Sparkenzap gave me the suggestion to check the false bulkhead and that was the problem. I changed it out and haven't had a problem since.
It is located on the Emgine Management Fusebox. It is on the outside of the box and has 2 heavy gauge wires going to it. One comes from the High Power Module in the trunk and the other wire goes to the starter.

The is a pic from a 97 donor car

 

BobRoy,

I have the problem and GGG's answer didn't work....Now you have a Photo of some Wires and Tubes .....and your answer is that you changed it out and haven't had a problem since .....I'm lost!! Could you elaborate a little more on what you actually did? I just don't get it? Which wire did you replace etc! ??? Sorry but I just don't get it!

Please! Billy Clyde @ Cinco Ranch

 

Here's another pic.


The false bulkhead ia a post, my idea of describing it, that the feed from the high power module in the trunk that Graham described and the cable going to the starter are attached. The post also feeds the Engine Compartment Fuse Box.
It has a plastic insulator that melted on my X308. It was probably due to a bad connection and the false bulkhead got hot and partially melted the isolator causing the intermittent no start.

I replaced the false bulkhead.

 

Hello BobRoy......I've got your photo and a short write-up about a POST that is on a False Bulkhead in the Engine Compartment of an X308! It's a nice Photo! But BobRoy, I don't have any idea what an X308 is or where this POST is...I assume .....it is under the Bonnet somewhere...Should I look on the Rt-Hand side of the Engine...The side the Starter is on or where would it be on a XKR? Just nudge me toward it...I know it's there but I'm a little slow! My Brain is still in the Boot......lead me under the Bonnet! I need to get this "sweet thing" running again!
Thanks! Billy Clyde

 

X308 is a Sedan. We have the X100... like all the cool kids do. I would love to see the location in an X100 engine bay.

 

What's up y'all... Hope this helps.

If you open the hood and go over to the RH side of the engine bay (pass side US car) you will see a plastic cover. It kind of tabs into a off square enclosure near the fire wall at the back corner of the engine. A "false" bulkhead... Inside, under that plastic cover you'll find a fuse box, starter relay, and the plastic case for the ECU... If you look OVER the edge, or run you hand on the OUTSIDE of this enclosure (the false bulkhead) between the cam cover and the outer wall of the bulkhead you will find the subject of that photo. It's often covered with a flip top style rubber boot. DONT rip it, it's useful and hard to find.

It's an insulated post (insulated from coming into contact and grounding on the body) that holds a major cable directly from the battery. It delivers 12v and HIGE amps at start up to the starter as well as delivers charge from the alt (thru the starter when it's at rest) to the battery. It's an important bit. 13mm nutt (don't drop it). Remove it and inspect and cleant the post, the volt face, the wire terminal and all that, then replace. Oh, the washer faces as well.

 

I ran into the same symptoms years ago, but with 3 Jags and a whole laundry list of electrical problems, I can't recall what to blame.

I'd plug in an ODBII tester, hook the battery charger on to get 14V for starting, verify system voltage on the tester, turn the key to the run position, wait about 5 seconds for all the dash lights to run their course, then hit the starter. If it doesn't start, I look to see what parameters are suspicious. Retry starting in neutral as the shifter and brake switches drove me crazy.

Good luck!

 

Checked and this was in good order.